1. Field of the Invention
The present invention relates to a method and system for charging a user (client) for obtaining access to a packet data network.
2. Description of the Prior Art
A user (person, PC and communications device, such as a telephone) typically obtains access to a packet data network, such as an IP network (internet), by connectivity provided by a corporate access network or a public internet service provider (ISP). The connectivity provided by the corporate access network or the ISP provides the user with a whole host of services which are billed to the user's account or to the company's account. These services are the same services the user wishes to access during roaming. In certain circumstances, when the user roams, such as when a roaming agreement exists between the user's home network and a wireless network to which the user roams, through which connectivity is made to a packet data network, all charges are handled automatically by the roaming agreement between the respective networks. As a result, billing consequent from the user's connectivity to the packet data network through the second network is handled seamlessly through the billing arrangement which the user has with the first network.
However, in some situations which are especially prevalent with wireless networks which provide users access to packet data networks, the typical user may wish to remain anonymous with respect to the second network which provides connectivity to the packet data network or when there is no roaming agreement in existence to bill the user between the user's home network and the network to which the user roams and through which the user is connected to the packet data network. In these circumstances, alternative billing arrangements must be made.
The GSM (Global System for Mobile Communications) telephony system uses algorithms in the mobile user units and in the network servers which control authentication of the user to prevent unauthorized access to the network and to provide encryption of the transmissions between users. The GSM System is described in depth in the publication, “The GSM System for Mobile Communications” by Mouly and Pautet, Copyright 1992, which publication is incorporated herein by reference in its entirety. Authentication in a GSM network is performed by the generation of a signed response SRES by both the user mobile and the network which is a function of a unique secret identifier Ki of the user mobile and a random number RAND. The signed response SRES is calculated in a subscriber identification module (SIM) based on Ki inside SIM and RAND obtained from the network authentication center (AUC). Additionally, the user mobile and the network each perform encryption by generating a ciphering key Kc, which is a function of the same random number RAND and the secret identifier Ki of the user mobile. The first authentication algorithm which calculates SRES is known as the A3 algorithm and the second algorithm which computes Kc, which is computed each time a mobile station is authenticated, is known as the A8 algorithm. However, each of the operations of authentication and computing of the ciphering key Kc requires the user mobile to be programmed to perform the aforementioned computations.